It is well known that orthogonal frequency division multiplexed (OFDM) systems divide a channel bandwidth into several narrowband subcarriers. Many modern OFDM system proposals include the capability to support frequency-selective (FS) resource allocation. During frequency-selective resource allocation, the channel bandwidth is divided into several sub-bands, which may be called tiles or resource blocks. Each resource block is used for a particular transmission over a particular time interval, and includes several adjacent OFDM subcarriers and spans multiple OFDM symbol periods. For example, a resource block in an OFDM system with a 15 kHz subcarrier spacing and a 4.76 us cyclic prefix length could be defined as containing 12 adjacent subcarriers (˜180 kHz), and the minimum time that a resource block can be assigned for could be seven OFDM symbol periods (˜0.5 msec).
A Discrete Fourier Transform (DFT) pre-coder can be applied to data prior to mapping the data onto the OFDM subcarriers. Such a modulation scheme is known as DFT-spread OFDM, or DFT-SOFDM. DFT-SOFDM can use resource blocks for transmission, similar to plain OFDM.
The use of resource blocks in OFDM or DFT-SOFDM enables data allocation to a particular user or mobile unit to be made on the resource block having the best channel quality. However, this requires the base station to determine which resource block has the best quality for the mobile unit, on either the downlink or uplink depending on whether the resource allocation is for receiving data or transmitting data. For frequency selective resource allocation on the downlink, a mobile unit can determine the downlink channel quality of various resource blocks by monitoring a wideband pilot channel on the downlink, which can be received and similarly used by all mobile units. However, for frequency selective resource allocation for the uplink, the base station will not be able to determine the necessary uplink channel quality information for a particular mobile unit unless the mobile unit transmits a wideband channel sounding pilot signal. The sounding pilot signal results in additional uplink overhead, and this overhead can become large when the number of active mobile units in a cell wanting to perform wideband channel sounding becomes large. Therefore, a need exists for a method and apparatus for performing resource allocation with lower required overhead than previous wideband channel sounding-based methods.